Repair of grub boot and default startup after Windows, Ubuntu dual system reinstall windows system

        Today, the children's shoes reload system, his computer is Windows, Ubuntu dual system, the system that needs to be reinstalled is windows, it is said that because many games only support 64-bit, you have to change to 64-bit ==... So I I installed a windows for him, and then re-booted Ubuntu, the following record: gurb boot repair: 1, take a Ubuntu system U disk or CD, if not, go to burn one, how to burn this article. 2, restart into the U disk or CD boot, select the utility Ubuntu (try ubuntu). 3. View the information. Open the terminal (ctrl+alt+t), enter [plain] sudo -i (for administrator privileges) fdisk -l (view partition and type) and then your disk information will appear. [plain] Device Boot Start End Blocks Id System Find the contents of the corresponding Device column in the row of 83 in the Id column to see how much sda is. The following assumes sda*. (If there are multiple 83 partitions with Id, you can try 4-6 steps from the back one by one). 4. Mount the partition. Enter in the terminal (note the replacement of * and spaces): [plain] mount /dev/sda* /mnt 5. In the terminal, type: [plain] grub-install --root-directory=/mnt /dev/sda Wait a moment You can see: Installationfinished, No Error Reported, indicating that the setup was successful. 6, restart the computer to see the Ubuntu grub boot interface, if not, please return to step 3 to see if there are multiple Id is 83 partition. 7, at this time do not enter windows, enter Ubuntu in the terminal to enter: [plain] sudo update-grub After restarting the computer can enter Windows and Ubuntu normally, then grub boot calculation is completed. The grub default startup item modification The classmate also asked to change the default startup item back to windows. . . (This way you can enter Ubuntu a few times...) Remember that windows is the first few lines of the startup item at startup. Enter Ubuntu, type in the terminal: [plain] sudo gedit /boot/grub/grub.cfg Change the default 0 of set default="0" to the window you just saw minus one in the first few lines. Save and exit, restart.